Towing vehicles such as trucks, motorhomes, etc. often tow trailers, powered vehicles, and other towed vehicles. As used herein, the term “trailer” encompasses anything that can be towed that does not have its own engine or other means of self-propulsion; the term “powered vehicle” encompasses anything that can be towed that includes its own engine or other means of self-propulsion; and the term “towed vehicle” may encompass a trailer or a powered vehicle.
Regulations in most states require any trailer over 3000 pounds to be equipped with brakes, such as electric trailer brakes, hydraulic surge brakes, or electric over hydraulic brakes. A trailer brake control system activates the trailer brakes in some manner based on inputs received either directly (electrical signal from the towing vehicle's brake lights) or indirectly (inertia created by the towing vehicle slowing).
Towing powered vehicles such as cars presents different braking challenges, because the powered vehicle typically has its own fully functioning hydraulic brake system rather than electric brakes. When towing a powered vehicle, a self-contained, self-activating braking system may be attached to a brake pedal of the powered vehicle to press against the brake pedal and operate its associated brakes. For example, an after-market master brake controller in the towing vehicle can tell a brake pedal activation device, such as a BRAKE BUDDY™, in the towed vehicle when to physically depress the brake pedal.
The after-market master brake controller is typically designed for communication with either a trailer or a powered vehicle, but not both, so as to provide optimum braking for the type of vehicle being towed. A powered vehicle's brake pedal activation device could be tuned to accept the input of a master brake controller designed for communication with a trailer, but doing so results in compromises for other braking applications. Master brake controllers exist that allow an operator to select between two different towed powered vehicle braking algorithms (fully proportional braking or threshold level braking for example) or two different trailer algorithms (trailer empty and trailer full being an example). However, no master brake controller exists that allows the operator to choose between a braking algorithm that has been especially designed for a trailer and an algorithm that has been especially tuned for a towed powered vehicle.
It may be desirable, in many instances, to provide information about a towed vehicle via a master brake controller mounted in a towing vehicle. For example, the operator may wish to have an indication whether the towed vehicle brakes are activated and to monitor the condition of the brake pedal activation device and the wiring thereof. This requires two-way communication between the master brake controller in the towing vehicle and the brake pedal activation device in the towed vehicle. One way to accomplish this is to communicate a status of the towed vehicle brakes by a radio frequency (RF) system. However, RF systems can be expensive, and random interference may result in erratic performance due to weather, construction of the towing vehicle and/or the towed vehicle, other equipment in the vicinity, and the like. Troubleshooting these interferences can be difficult and time-consuming.
Another method of establishing two-way communication between the master brake controller in the towing vehicle and the brake pedal activation device in the towed vehicle is to run an additional wire between the master brake controller and the towed vehicle. However, running this extra wire is time-consuming, adding an additional step for the operator, who must now connect one mechanical and two electrical links between the towed vehicle and the towing vehicle (i.e., a breakaway switch cable, a master brake controller feedback wire, and a towed vehicle lighting/power connector, such as a 7RV connector).
Many brake pedal activation devices are configured to apply a certain amount of air pressure, vacuum, or current to a force generation device for providing physical force to the brake pedal of the powered vehicle being towed. For example, the brake pedal activation device may provide 50 psi of air pressure to a pneumatic cylinder to press or pull the brake pedal of the powered vehicle. Other systems are configured to physically move the brake pedal a predetermined distance, while others measure current supplied to an electric motor or actuator. However, none of these approaches directly determines what force is applied to the brake pedal of the powered vehicle. This can be problematic, since each powered vehicle has a different brake pedal design with a different amount of sensitivity and resistance.
In one brake pedal activation device, a pressure regulator and a limit switch are mounted on the end of a pneumatic cylinder, providing a shutoff point once a preset force on the brake pedal has been reached. However, this does not measure the applied force over a full range of its application, which severely limits this brake pedal activation device's ability to determine a proper application of force. For example, if the brake pedal attachment failed, this type of brake pedal activation device may never reach its shutoff point and would remain unaware of the failure.
The towed vehicle lighting/power connector mentioned above typically consists of several individual insulated wires combined into a cord for transferring multiple electrical functions, such as tail lights and brake lights, from the towing vehicle to the towed vehicle. The cord may have plugs on either end for plugging into outlets mounted to the towing vehicle and to the towed vehicle, electrically coupling the two. This allows the cord to be removed from both the towing vehicle and the towed vehicle when they are being used independently, thus reducing the risk of damaging the cord.
In addition to the lighting/power connector cable, some laws mandate that brakes of the towed vehicle be applied if the towed vehicle is separated from the towing vehicle while traveling on public roads. This is generally achieved by mounting a breakaway switch on the towed vehicle. This breakaway switch is normally closed and is held open by a plunger. This plunger is attached to the towing vehicle by a metal cable. If the towed and towing vehicles separate by more than a distance of this cable, the plunger is pulled out of the breakaway switch, causing the breakaway switch to close. A system in the towed vehicle senses the change of the breakaway switch from open to closed and activates the brakes of the towed vehicle. This type of breakaway switch suffers from two major shortcomings. One is simply that operators often do not use it, because they do not wish to take the time to connect the metal cable to the towing vehicle. Another is that the breakaway switch is often mounted in a position prone to damage and corrosion.